BES3 Italian Collaboration
BESIII is an experiment running at the Beijing electron-positron collider (BEPCII), based at the IHEP laboratory of the Chinese Academy of Sciences.
The collider BEPCII is a multibunch machine (inter-bunch interval 8 ns) designed to operate in the total energy range 2-4.2 GeV in the laboratory center of mass, at design total beam currents of 910 mA for both beams. The expected luminosity of BEPCII, optimized at the one-beam energy of 1.89 GeV, is 1×1033cm-2s-1. Construction started in 2004 and commissioning went through 2 phases: in 2006, with the interaction region run on conventional magnets, and 2007, when superconducting quadrupoles were installed. During these periods the machine gave data-taking time to Synchrotron Radiation experiments.
Installation of the BESIII detector started in March 2008, and data taking followed on March 6 2009, with a scan of the ψ(2S) peak. During the next month, as machine commissioning continued, the peak luminosity of BEPCII increased steadily from 1.4 to 2.3×1032 cm-2s-1, with beam currents of 550 mA for both electrons and positrons, reaching a new record of 6×1032 cm-2s-1 in February 2011 with currents close to 700 mA.